dentin

Question 1

dentin does not have

Answer 1

b.v, whole cells

Question 2

dentin has

Answer 2

odontoblast process and nerve endings

Question 3

dentin has a greater ____ than enamel

Answer 3

compressive strength

Question 4

dentin cushions…

Answer 4

overlying enamel. so conditions that affect dentin also affect enamel (DI)

Question 5

dentin takes what configuration at the DEJ?

Answer 5

scalloped…this facilitates adhesions

Question 6

what stage of odontogenesis does dentinogenesis occur

Answer 6

bell stage

Question 7

what happens in the late bell stage

Answer 7

1. inner epithelial cells differentiate into ameloblasts
2. mesenchymal dental papilla cells differentiate into odontoblasts
3. dentin secreted
4. enamel secreted

Question 8

in what direction does dentinogenesis go

Answer 8

cusp tips to cervix and from periphery to pulp center

Question 9

what induces odontoblast differentiation

Answer 9

signal secreted from enamel organ/enamel knot (signaling or growth factors)

Question 10

what is one molecule though to play a part in odontoblast differentiation

Answer 10

Wnt10a. 1st expressed in the enamel knot, then in pre-odontoblasts at the cusp tip and then cervical. Expression immediately precedes the wave of odontoblast differentiation

Question 11

supporting evidence that Wnt10a induces…

Answer 11

Dentin sialophosphoprotein (secreted by mature odontoblasts)

Question 12

what is the unmineralized organic matrix of dentin called

Answer 12

predentin

Question 13

requirements for mineralization of dentin

Answer 13

1. Ca and Phosphate

2. initiation of crystal formation (by 2 mechanisms)

Question 14

where does the phosphate for dentin mineralization come from

Answer 14

plasma and cleavage of organic molecules containing phosphate in odontoblasts by alkaline phosphatase

Question 15

2 stages of dentin formation

Answer 15

1. mantle

2. circumpulpal

Question 16

mantle dentin formation

Answer 16

principle component of matrix= collagen type 1 (large fibrils)
secreted from odontoblasts
procollagen secreted is oriented at right angles to DEJ
matrix vesicles (Ca and PO crystals)

Question 17

circumpulpal dentin formation

Answer 17

smaller type I collagen fibrils, parallel to basal lamina/DEJ
proteins synthesized and secreted from odontoblast (with Ca and P ions) processes that bind to collagen and precipitate it out to form crystals

Question 18

differences b/w mantle and circumpulpal dentin

Answer 18

mantle dentin more organic, mantle dentin less mineralized, so DEJ more vulnerable to caries

Question 19

dentin phosphoprotein

Answer 19

highly phosphorylated, high in serine/aspartic acid, acidic and anionic, long chain of polar a.a…hypothesis is that it precipitates Ca ions from tissue fluid which initiates mineralization. gene is DSPP which is cleaved into DPP

Question 20

mineral phase of dentin

Answer 20

hydroxyapetite with 4-5% carbonate…crystal size is smaller than enamel with random orientation

Question 21

organic phase of dentin

Answer 21

processes of cells, extracellular matrix

Question 22

extracellular matrix of dentin has

Answer 22

collagen type I (90%) and non-collagenous proteins (non specific, mineralized tissue specific, dentin dominant)

Question 23

dentinogenesis imperfecta

Answer 23

dentin forms improperly…mutations in DSPP. dominant negative mutation (mutated DSPP traps normal protein)

Question 24

mutations in DSPP

Answer 24

1. changes in 1st 3 a.a are critical for moving DSPP though the RER (stuck in RER)
2. base pair deletions causing a frameshift in polar a.a region…changes it from polar to uncharged (stuck at cell membrane)

Question 25

contents of dentinal tubule

Answer 25

fluid, nerve fibers, odontoblastic processes

Question 26

dentinal tubules are

Answer 26

@ right angles to the DEJ, s-shaped at the crown, straighter in the root, more branching at the DEJ than the DCJ

Question 27

of dentinal tubules in greater...

Answer 27

in inner dentin compared to outer

Question 28

the diameter of tubules is greater...

Answer 28

in inner dentin. tubules occupy less room at the DEJ that DPJ. permeability and wetness increase towards the P-D border

Question 29

primary dentin

Answer 29

formed until completion of root development, most dentin, mantle and circumpulpal dentin (more mineralized)

Question 30

secondary dentin

Answer 30

formed after root development, slower rate, throughout life, along entire circumference of the pulp chamber (heaviest on the roof and floor)

Question 31

tertiary/reparative dentin

Answer 31

produced in specific location in response to noxious stimuli, irregular, under caries

Question 32

intertubular dentin

Answer 32

b/w tubules, large volume, less mineralized

Question 33

intratubular/peritubular dentin

Answer 33

lining tubules, smaller volume, greater mineralization, ring is wider near DEJ

Question 34

translucent/sclerotic dentin

Answer 34

tubules completely filled with intra/peritubular dentin...translucent (process of aging) and sclerotic (accelerated deposition due to caries/attrition). increases with age

Question 35

dead tracts

Answer 35

tubules dried out and filled with air

Question 36

intraglobular dentin

Answer 36

hypomineralized dentin just below mantle dentin

Question 37

individual foci of calcification that fuse are called

Answer 37

calcospherites...if they don't fuse= interglobular dentin

Question 38

tome's granular layer

Answer 38

hypomineralized dentin at the periphery of the dentin near the CEJ

Question 39

growth lines of dentin are called

Answer 39

lines of von ebner ...exaggerated due to tetracycline